PubMed Health⌕ Search

Biomedical subjects

M E Campbell

Publications and source records attributed to M E Campbell.

At least 19 recordsLinked to original sources
PubMed1991

Activation of gene expression by human herpesvirus 6 is reporter gene-dependent.

Infection with human herpesvirus 6 (HHV-6) was found to up-regulate expression of human immunodeficiency virus and human T cell leukaemia virus type I (HTLV-I) long terminal repeat sequence (LTR), and herpes simplex virus type 1 (HSV-1) gD chloramphenicol acetyltransferase (CAT) constructs transfected into the T cell line, J. Jhan. Activation by HHV-6 was due to one or more viral proteins produced early in infection and, in the case of the HTLV-I LTR, was synergistic to induction mediated by the HTLV-I tax gene product. Neither the HTLV-I enhancer nor basal promoter elements of the HSV-1 gD gene were essential for activation and no increase in accumulated HTLV-I mRNA was observed due to HHV-6 infection. Induction by HHV-6 was found to be dependent on the reporter construct used, because the CAT gene and, to a lesser extent, the HSV-1 thymidine kinase gene were responsive to HHV-6 infection although no significant activation of growth hormone constructs was observed. Our results bear a strong resemblance to those obtained for the Epstein-Barr virus BMLF1 gene, indicating that the major HHV-6 trans-activator may be a homologue of this gene.

Chloramphenicol O-Acetyltransferase↗
PubMed1990

Conversion of Pseudomonas aeruginosa to the phenotype characteristic of strains from patients with cystic fibrosis.

Isolates of Pseudomonas aeruginosa from cystic fibrosis patients are unusual; they are often susceptible to the bactericidal effect of human serum, have a rough lipopolysaccharide, and produce an exopolysaccharide that is responsible for the characteristic mucoid phenotype. In contrast, strains from the environment and from patients with other diseases usually have smooth lipopolysaccharide, do not produce very much mucoid exopolysaccharide, and are phenotypically nonmucoid. The predominance of mucoid strains of P. aeruginosa in infections of patients with cystic fibrosis has not been explained. In the lower airways, where P. aeruginosa persists in cystic fibrosis, nutrients for bacterial growth may be limited. We investigated whether growth of P. aeruginosa under conditions of suboptimal nutrition causes conversion to the characteristic cystic fibrosis phenotype. Ninety-two strains of P. aeruginosa were maintained for up to 90 days in a minimal medium with acetamide as the sole carbon source. In 56 (52%) of 107 cultures, isolates with rough lipopolysaccharide emerged, and in 20 (19%) of 104 nonmucoid cultures, mucoid isolates were recovered. Strains with rough lipopolysaccharide also were sensitive to the bactericidal effect of normal human serum. Under conditions of suboptimal nutrition in vitro, isolates of P. aeruginosa emerged that produced rough lipopolysaccharide and were mucoid, typical of many isolates from cystic fibrosis patients. This peculiar phenotype may arise as a consequence of nutritional limitation within the cystic fibrosis respiratory tract rather than from features unique to these strains of bacteria.

Blood Bactericidal Activity↗
PubMed1989

Use of a pilin gene probe to study molecular epidemiology of Pseudomonas aeruginosa.

Strains of Pseudomonas aeruginosa from patients with cystic fibrosis (CF) are unusual. The majority have a rough lipopolysaccharide (LPS) which renders them nontypeable by conventional typing systems based on a serological reaction with the O polysaccharide of smooth LPS. We developed a new typing scheme using a pilin gene probe as a marker for hybridization with endonuclease-digested genomic DNA from P. aeruginosa. Twenty-one different restriction fragment length polymorphism (RFLP) types were found among 249 isolates. RFLP type 7 was recovered only from patients with thermal burns (9 of 14 isolates) in both Vancouver, British Columbia, and Edmonton, Alberta, Canada. None of the other RFLP types showed a clear predilection for disease state or environmental niche. Multiple morphologically different isolates from individual patients with CF were studied; each isolate in 33 of 40 sputum samples had an identical RFLP type, despite considerable LPS serotype heterogeneity. Sequential isolates from 23 patients were studied; in 10 isolates there was a clear change in both the RFLP and the LPS serotype. We conclude that patients with CF usually harbor a single P. aeruginosa RFLP type in their sputa, but that one strain can replace another as the predominant colonizing type.

Bacterial Outer Membrane Proteins↗
PubMed1989

Continuous increase in blood lactate concentration during different ramp exercise protocols.

The applicability of a continuous model description of the blood lactate concentration [( La-]) vs. O2 uptake (VO2) relationship was studied in nine healthy male volunteers during three different ramp exercise protocols. The work rate was increased at either 8, 15, or 50 W/min. The continuous model for [La-] = â + b exp(ĉVO2) was compared statistically with a previously proposed log-log transformation model for the [La-] and VO2 variables. It was found that the mean square error was significantly less for the continuous as opposed to the log-log model (P less than 0.01) by analysis of variance pooled across all three ramp slopes. The mean square errors from the individual ramp slopes were also significantly less for the continuous model by paired t test (P less than 0.05). It was observed that the major contributor to the increased error of the log-log model was at VO2's at or above the intersection point (lactate threshold) of the two linear log-transformed segments. The log-log transformation does not appear to relate to any physiological process. The lactate slope index, taken as the point where the slope of the relationship between [La-] and VO2 (i.e., d[La-]/dVO2) equaled 1, occurred at a mean VO2 of 2.25 and 2.37 l/min for the 15- and 8-W/min ramp slopes, respectively, but at 2.76 l/min for the 50-W/min ramp (P less than 0.05). It is concluded that [La-] increases as a continuous function with respect to VO2 across a wide range of ramp work rate slopes.

Adult↗
PubMed1988

A complex formed between cell components and an HSV structural polypeptide binds to a viral immediate early gene regulatory DNA sequence.

Transcription of HSV immediate early genes is stimulated by a virus structural protein, Vmw65, in a process that requires specific recognition of the sequence TAATGARAT (R = purine). Upon incubation of nuclear extracts of HSV-infected cells with a short DNA fragment containing TAATGARAT, a novel virus-induced protein-DNA complex (named IEC) was detected. Addition of virion extract, containing Vmw65, to nuclear extract from uninfected cells also resulted in the formation of IEC. Vmw65 is a component of IEC, which contains proteins bound specifically to TAATGARAT. Thus, Vmw65 and cellular factors combine to form a sequence-specific DNA-binding complex. This system provides a model for studies of the regulation of inducible cellular genes.

DNA, Viral↗
PubMed1988

New selective medium for Pseudomonas aeruginosa with phenanthroline and 9-chloro-9-[4-(diethylamino)phenyl]-9,10-dihydro-10- phenylacridine hydrochloride (C-390).

A new selective medium (PC agar) for the isolation of Pseudomonas aeruginosa was developed, consisting of 30 micrograms of 9-chloro-9-[4-(diethylamino)phenyl]-9,10-dihydro-10-phenylacridine hydrochloride (C-390) per ml and 30 micrograms of phenanthroline per ml in Columbia agar. PC agar was superior to phenanthroline, C-390, acetamide, and cetrimide agars for the selective growth of P. aeruginosa.

Acridines↗
PubMed1987

Biotransformation of caffeine by microsomes from human liver. Kinetics and inhibition studies.

The nature of the cytochrome P-450-dependent enzyme reactions giving rise to four primary metabolites of caffeine was investigated using microsomes isolated from livers of human kidney donors. Metabolite formation proceeded at a lower rate than that predicted from in vivo caffeine elimination half-lives, as has been observed in other species using this compound as a substrate in microsomal incubations. Kinetic experiments indicated that the formation of each of the N-demethylated metabolites paraxanthine, theobromine and theophyline was mediated by both a high- and a low-affinity catalytic site over a substrate concentration range from 0.05 mM to 80.0 mM, although only the high-affinity component is likely to be of any importance at normally encountered in vivo caffeine concentrations. 7-Ethoxyresorufin and acetanilide, selective substrates for two polycyclic aromatic hydrocarbon (PAH)-inducible isozymes of cytochrome P-450 in the mouse (P1-450 and P3-450, respectively) were each able to inhibit competitively the formation of caffeine metabolites by human liver microsomes, while caffeine could in turn similarly inhibit the biotransformations of these two compounds. The isozyme-selective P-450 inhibitor alpha-naphthoflavone (ANF) potently inhibited the high-affinity component of caffeine N-demethylations, while 1-phenylimidazole (PI) was a more potent inhibitor of the low-affinity component. The inhibition studies also indicated that the formation of 1,3,7-trimethyluric acid was mediated by both ANF-sensitive and PI-sensitive sites. Taken together, the data support suggestions from in vivo studies that a PAH-inducible isozyme of cytochrome P-450 plays a significant role in the biotransformation of caffeine in man.

Adult↗
PubMed1987

DNA sequences which regulate the expression of the pseudorabies virus major immediate early gene.

It has been shown previously that the transcription of herpes simplex virus (HSV) immediate early (IE) genes is transactivated by a component of the virus particle. The trans-inducing factor (TIF) is known to be polypeptide Vmw65. Infection with pseudorabies virus (PRV), a related herpesvirus, does not increase expression from HSV IE regulatory sequences (W. Batterson and B. Roizman, 1983, J. Virol. 46, 371-377). To examine the control of the PRV IE gene and possible sequence specificity of a TIF, the 5' terminus of the PRV major IE transcript was mapped and hybrid plasmids containing PRV upstream sequences linked to the HSV-1 TK gene were constructed. Gene expression under the control of PRV IE or HSV-1 IE gene 3 upstream regions were compared using transient expression assays. It was found that infection with uv-irradiated PRV did not stimulate expression from PRV IE or from HSV-1 IE gene 3 upstream regions, indicating that PRV did not possess an effective TIF. Infection with uv-treated HSV-1, or cotransfection with a plasmid which encodes Vmw65, stimulated expression from both PRV and HSV IE gene upstream regions. The nucleotide sequence of the 5' end of the PRV transcript and its upstream region was determined. This region was, in overall structure, unlike the upstream regions of HSV IE genes but showed a strong similarity to the enhancers of human and murine cytomegaloviruses (HCMV and MCMV). In particular, a reiterated 15-bp element of the PRV upstream region was homologous to a conserved, repeated sequence element found in both HCMV and MCMV enhancer regions and was also related to the "TAATGARATTC" motif found upstream of all HSV IE genes. Thus a conserved sequence element occurs upstream of IE genes in four herpesviruses with different genome structures and diverse biological properties.

Animals↗
PubMed1987

Hospital epidemiology of Pseudomonas aeruginosa from patients with cystic fibrosis.

Pseudomonas aeruginosa colonizes the respiratory tract of most older patients with cystic fibrosis. The means by which these bacteria are acquired and the risk for patient-to-patient spread among subjects with cystic fibrosis are poorly understood. We studied the spread of Ps. aeruginosa within a hospital environment. Pseudomonas was rarely recovered from the inanimate environment surrounding patients with cystic fibrosis or from hand or rectal cultures of patients who were colonized in the oropharynx. There was transient cross-colonization with Ps. aeruginosa between patients with cystic fibrosis sharing a hospital room in three of seven pairs studied. In all cases the "new" isolate was recoverable only once and was not found during a 2-year follow-up. Three of four sibling pairs with cystic fibrosis shared the same Ps. aeruginosa serotype(s). The risk of sustained cross-colonization by Ps. aeruginosa between patients with cystic fibrosis appears to be minimal, except under conditions of prolonged close contact.

Adolescent↗
PubMed1987

A urinary metabolite ratio that reflects systemic caffeine clearance.

Systemic caffeine clearance and urinary metabolite profiles were determined in 15 subjects with diverse exposure histories to cytochrome P-450 inducers (cigarette smoke) and inhibitors (oral contraceptive steroids). A correlation was observed between caffeine clearance and a urinary ratio based on the molar recovery of paraxanthine 7-demethylation products relative to a paraxanthine 8-hydroxylation product (r = 0.91; P less than 0.001). Analysis of urinary metabolites was undertaken in a larger population to assess the effects of gender, age, oral contraceptives, and smoking on the ratio. No gender differences were observed in either adults or children; children (n = 21) showed a higher (P less than 0.001) mean metabolite ratio than adults (n = 61), oral contraceptive users (n = 9) had lower (P less than 0.05) ratios than women not taking oral contraceptives (n = 30), and smokers (n = 26) had higher (P less than 0.001) ratios than nonsmokers (n = 61). The data indicate that a urinary metabolite ratio based on paraxanthine 7-demethylation/8-hydroxylation products reflects systemic caffeine clearance and likely monitors cytochrome P-450 activity inducible by polycyclic aromatic hydrocarbons.

Adult↗
PubMed1987

The 65,000-Mr DNA-binding and virion trans-inducing proteins of herpes simplex virus type 1.

The possible identity of the herpes simplex virus type 1 (HSV-1) 65K (65,000-Mr) virion protein which stimulates transcription from immediate-early genes with the HSV-1 65K DNA-binding protein was investigated. The two proteins were found to be distinct by the three separate criteria of immunological reactivity, tryptic peptide fingerprinting, and mobility in two-dimensional gels. Using HSV-1/HSV-2 intertypic recombinants and a serotype-specific antiserum, we located the gene encoding the 65K DNA-binding protein between coordinates 0.574 and 0.682 on the HSV-1 genome. The protein is posttranslationally modified by phosphorylation. In crude extracts of HSV-1-infected cells the 65K trans-inducing protein did not detectably bind to double-stranded calf thymus DNA under the conditions of our assay.

Antigens, Viral↗
PubMed1986

Effect of allopurinol on caffeine disposition in man.

Caffeine (5 mg kg-1) was administered orally to two healthy, non-smoking subjects on three separate occasions--before, and during therapy with the xanthine oxidase inhibitor allopurinol at doses of either 300 or 600 mg daily. Plasma and urinary levels of methylxanthines, endogenous oxypurines and allopurinol and its metabolite oxypurinol were measured using h.p.l.c. analyses. Allopurinol treatment caused a specific, dose-dependent inhibition of the conversion of the caffeine metabolite 1-methylxanthine (1X) to 1-methyluric acid (1U). A good correlation was observed in both subjects between the urinary 1U/1X molar ratio and the ratio of endogenous urate to hypoxanthine + xanthine at the different allopurinol doses, supporting the proposal that the 1U/1X molar ratio after caffeine intake provides an in vivo index of xanthine oxidase activity in man.

Adult↗
PubMed1985

In-vitro activity of pefloxacin compared to enoxacin, norfloxacin, gentamicin and new beta-lactams.

The in-vitro activity of pefloxacin was compared with that of norfloxacin, enoxacin, nalidixic acid, gentamicin, cefotaxime, ceftazidime and, where appropriate, other beta-lactams against a total of 363 recent clinical isolates. An agar dilution procedure was used to determine MICs and two inocula (10(4) and 10(6) cfu) were used throughout. Pefloxacin inhibited 90% of isolates of Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, indole-positive Proteus spp., Enterobacter spp., Shigella sonnei, Salmonella typhi, Campylobacter jejuni, Staphylococcus aureus and Haemophilus influenzae at less than or equal to 0.5 mg/l. Serratia marcescens and Providencia stuartii were somewhat more resistant, 2 mg/l of pefloxacin being required to inhibit 90% of isolates of these species. Pefloxacin inhibited 90% of isolates of Pseudomonas aeruginosa at 4 mg/l and 90% of isolates of the Bacteroides fragilis group at 16 mg/l. The activity of enoxacin was similar to that of pefloxacin, with enoxacin being four-fold less active against Staph. aureus, two-fold less active against the Bacteroides fragilis group and most species of the Enterobacteriaceae, and two-fold more active against Ps. aeruginosa. Pefloxacin showed good activity against gentamicin-resistant Ps. aeruginosa and Enterobacteriaceae and against methicillin-resistant Staph. aureus. Strains with decreased susceptibility to norfloxacin tended to be less susceptible to both pefloxacin and enoxacin.

Anti-Bacterial Agents↗
PubMed1975

Influence of nutrition on the crimping rate of wool and the type and proportion of constituent proteins.

When the nutritional level of sheep is restricted, the staple crimp frequency of the resultant fleece increases substantially whereas the cystine and high-sulphur protein contents decrease. This is in marked contrast to the direct relationship between crimp frequency and cystine content among sheep. These observations can be reconciled by assuming that variations in crimp frequency are attributable solely to a combination of follicle shape and fibre length growth rate without recourse to the more generally accepted theories relating to the proportion and distribution of ortho- and paracortical cells in the firbre cortex. The major portion of the decrease in the cystine content of high-crimp wools is due to the decreased synthesis of a specific protein fraction (ultra-high-sulphur protein) as would be expected from the results of dietary supplementation experiments. Low-crimp wools do not appear to contain this protein fraction and in this respect they may differ from high-crimp wools.

Amino Acids↗